We analyzed the heavy metal content in the muscular tissue of the catfish, Ariopsis felis, in the southern Gulf of Mexico between 2001 and 2004. The research was done in order to establish an environ- mental frame of reference for this organism. The metal concentration was as follows: Hg < Co < Pb < Ni < V < Cr. Cobalt and vanadium contents were found to decrease and those of nickel, mercury, and chromium to in- crease; however, neither of these trends was observed for the lead content. One-way analyses of variance con- firm significant temporal variation only for cobalt, mercury, lead, and vanadium. Significant linear correlation coefficients (p ≤ 0.05) were found for Co-V, Cr-Ni, Cr-Pb, Co-Hg, Ni-V, and V-Pb. The first three associa- tions showed positive correlations, whereas the remaining ones had negative correlations. A factor analysis grouped the studied metals depending on their origins. The metal levels found in the muscular tissue of A. felis from the southern Gulf of Mexico were lower than those set by national and international regulations.